Turbine power plant fuel control utilizing speed, temperature and compressor pressure



2,822,666 TURBTNE POWER PLANT FUEL CONTROL UTTLIZING SPEED, TEMPERATURE AND COMPRESSOR PRESSURE Filed Aug. 31, 1951 S. G. BEST 4 Sheets-Sheet l Feb. 11, 1958 Feb- 1l, 1958 s. G. BEST 2,822,666

TURBINE POWER PLANT FUEL CONTROL UTILIZING SPEED, TEMPERATURE AND COMPRESSOR PRESSURE Filed Aug. 31, 195] 4 Sheets-Sheet 2 Q PUMP ma f r Pu 0 r S 00N TROL /30 S. G. BEST Feb. l1, 1958 2,822,666

TURBINE POWER PLANT FUEL CONTROL UTILIZING SPEED, TEMPERATURE AND COMPRESSOR PRESSURE Filed Aug. 31.,v 1951 4 Sheets-Sheet 3` GOVERNOR [avra/r aw in r Siae-d '1415/ 6,', l5 es?! MZ'oa/ney R O N m V 0 G Feb. 11, 1958 s. G. BEST 2,822,656

TURBINE POWER PLANT FUEL CONTROL UTILIZING SPEED, TEMPERATURE AND COMPRESSOR PRESSURE Filed Aug. 3l, 1951 4 Sheets-Sheet 4 United States Patent si TURBINE POWER PLANT FUEL CONTROL UTlLIZlNG SPEED, TEMPERATURE AND COMPRESSOR VvPRESSURE Stanley G. Best, Manchester, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application August 31, 1951, Serial'No. 244,551

59 Claims. (Cl.'60-39.28)

This invention relates to vfuel controls and more specifically to fuel controls for gas turbine power plants.

It is an object of this invention to provide a fuel control for turbine power plants comprising a hydro-mechanical system which is free of sticking, and rugged while at the same time providing accurate fuel control.

VIt is a further object of this invention to provide a fuel control utilizing power plant speed, inlet air temperature and compressor pressure asparameters of power plant operation for controlling the iiow of fuel.

It is another object of this invention to. providea fuel control which is readily adaptable for control of turbojet, turbo-prop or variable exhaust turbo-jet power plants with only minor modification and adjustment ofthe syslem.

These and other objects of this invention will become readily apparent from the following detailed description of the drawings in which:

Fig. 1 is a schematic illustration of a turbol power plant with a schematically indicated fuel control operatively connected thereto.

Fig. 2 is a diagrammatic illustration of the fuel control of 'this 'invention arranged for a turbo-jet power plant.

Fig. 3 is a detailed illustration of the compressor pressure servo mechanism.

Fig. 4 is a diagrammatic showing illustrating the .fuel control of this invention as modified for a turbo-prop 'power plant.

Fig. 5 is a schematic showing of a temperature compensating mechanism for the fuel -control.

pressor alone in the case Vofa turbo-jet power plant and to'also driveapropeller 22 in the case of a turbo-prop power plant.

Where the Vpower plant is of the turbo-prop type the AYusual variable pitch blades may be used to be controlled by a speed governor which can be set by apilots lever as `schematicallyillustrated. For normal operation the propeller would have a low pitch stop-as is Well-known inthe art.

The 'fuel control 26 senses the Values Aof Vthe same `parameters of power plant operation whether utilized with a turbo-jet ora turbo-prop. As illustrated'in4 Fig. 1, the fuel control senses R. P. M.`of the power plant, com- .pressor inlet temperature and compressor outlet pressure.

A pilots control-lever 30 is operatively connected to the fuel'control 26 for proper regulation thereof whiler fuel under pressure enters the fuel control and from there is -fe'dto the fuel nozzlesatthe combustion section of the -powerplant.

Fig. '2 diagrammatically villustrates Ithe`fu`el `control of l thisinvention for a turbo-jet power plant, Fundamen,

ICC

2 tally this fuel control provides'two signals which correspond to compressor pressure and speed, respectively, and multiplies these signals through linkages to position a throttle valve. A Vconstant pressure drop is 'maintained across lthe throttle valve so thateach position of the valve corresponds to a definite fuel flow. Signals corresponding to engine speed and compressor inlet temperature are fed through a three dimensional cam to override the normal control and vary throttle valve opening in mixed relation with compressor pressure to limit fuelflow accordingly.

The use of compressor pressure as a controlling parameterhas several distinct advantages over the use, for example, of inlet pressureto thepower plant.

.First therevis better protection againstba'ttle damage. If a bullet hole is made lin the compressor so air is ybled olf in large quantity, the compressor pressure falls off and cuts back fuel flow, preventing overheating of the engine. With a control based on inlet pressure, the control would notrecognize the damage'and would continue'feeding in fuel at the same rate as-before, which would overheat'the engine because of the reduction in air flow through the burners. Second, along the same line, the temperature limitingis still very nearly correct when lair is bled olf the compressor Afor operating accessories, whereas it wouldnot be in the case of a control based on inlet pressure. Third, greater consistency can be expected,:since absolute pressure at the turbine nozzles, whichis substantially equal to compressor discharge pressure, is, at a given limiting turbine inlet temperature and normal choked nozzle conditions, the single factor which directly determines mass air flow through the engine. Inletpressure determines mass flow in a .much more indirect manner. Fourth, the Heffects of Variations inspeed and ternperature are reducedradically so`that accurate measurements of these quantities are not required and design of the three dimensional cam is greatly simplified.

Referring to Fig. 2,-a low pressure pump 50fand a high pressure pump 52 maybe provided as well as a relief valve 54 for the low pressure stage "and -a relief valve156 for the high pressure fstage. A filter 60 is provided prior to the entry of the fuel into the system and this filter may include a. spring 62 to permit by-pass of the fuel when a predetermined pressure across the tilter obtains. lny the event of filter clogging the pressure 'will'raise 'the filter 60 against spring `|52so that'fuel will flow around the filter. High pressure fuel enters the line 66 toithe inlet chamber 68 of a throttle valve generally indicated at 70. As the throttle valve is opened fuel passes through the chamber 68 to the chamber 72 and then to the line 74 leading to the nozzles of the power plant. lA T 75 in the line 66 leads to afpressure regulator valve '76 which includes a chamber 78 anda chamber80 separated by a diaphragm 82. The chamber 80 ofthe pressure regulator valve 76 communicates via a line 84 withthe outlet side of the throttle valve, i. e., the chamber 72. The chamber 78 is under pressure equivalent to the inlet pressure to -the throttle valve. The spring Sbiases the valve toward a Aclosed position and the relative strength of this spring and the force responsive areas at opposite ends of the pressure regulatorvalve 76 determine the fixed pressure drop while will be maintained across the throttle valve. Any fuel that is hyp-passed bythe pressure regulator valve'iscarried back to the inlet of the pump-'52 via the line 88. It will of course be understood that-'the throttle valve 70 will have fixed maximum and .minimum opening stops incorporated therein.

The Vthrottle valve 70 is biased toward'a closed positionrby a spring 'whichbears against anenlargedfupper portion 92 of the movable 'elementof the valve. Motion is imparted tothe movablevalve element by means of a ivoted arm 10G which has its free end engaging a moy? able knife edge 102. interposed between the arm and the valve head 92 is a roller 104 which is carried by a reciprocating rod 106 which in turn is moved by a piston 110 of the main servomotor. The mechanism consisting of the arm 100, the roller 104 and the knife edge 102 is arranged to multiply the motion of the knife edge 102 and the roller 104 as reciprocated by the rod 106.

The knife edge 102 moves in a predetermined direction linearly with compressor pressure but after a predetermined pressure has been reached the knife edge` 102 moves in the opposite direction linearly with continued increase` in compressor pressure to provide a maximum pressure limiter by reducing fuel ow after the preselected pressure has been reached. The mechanism providing this type of movement will be described immediately hereinafter.

Compressor discharge pressure is admitted internally of a bellows which has its free end engaging an arm 122 which is fixed to and pivots about the axis of a rod 124. A second bellows 126 is evacuated and acts in opposition to the bellows 120 thereby providing motion to the arm 122 as a function of absolute pressure in the compressor. Motion of the arm 122 is transmitted via the rod 124 to another arm 128 which engages a pivoted member 130. The arm 130 in turn transmits motion to the compressor pressure servo system generally indicated in Fig. 2 as 134 and illustrated in better detail in Fig. 3.

As was previously mentioned, the compressor pressure servo mechanism 134 and its knife edge 102 operates so as to increase or decrease throttle valve setting by increasing or decreasing its eiect on the multiplying linkage. Referring to both Figs. 2 and 3, the operation of the compressor pressure servo system is best described in the following manner. As compressor pressure increases the arm 122 and likewise the arm 128 will be urged in a i downward direction. This causes downward movement of a movable valve element so that the port 142 will communicate with the port 144 so that high pressure fuel from the chamber 146 will iiow to the chamber 148 adjacent the top of the movable valve element 140. High .element will cover the port 156 so that any further movement of the movable valve element 140 in a downward direction will cause port 156 to be placed in communication with port 158 via the annulus 160 so that fuel in chamber 148 will be connected to the line 164 leading to the drain line 166. When the chamber 148 is subjected to drain pressure the higher pressure in chamber 146 will tend to move the main body portion and its accompanying knife edge 102 in an upward direction in direct response to continued increase in compressor pressure. This in turn causes a decrease in fuel flow by closing the throttle valve.

Normal control of the roller 104, the rod 106 and the servo piston 110 is determined by a speed signal which is obtained from a flyball speed governor 180. The governor is driven by a drive shaft and, depending upon the off-speed condition, the governor positions a pilot valve 182. High pressure fuel is admitted to the valve 182 via a line 184 while low pressure fuel or drain pressure exists in the chamber 186 within the body of the governor 180. It is then apparent that movement of the valve 182 to the left will cause high pressure fluid to flow in the line 183 through the port 190 of a second pilot valve 192 thence to the annulus 194 and line 196 and then to chamber 198 to move the piston 110V toward the left. Under these conditions, although both ends of they piston 110 are subjected to high pressure, the area of theright-hand side of the piston 110 is larger than the left-hand side; therefore, motion to the left results. Motion of the piston 110 to the left causes a decrease in fuel ow through the throttlevalve. The decrease in fuel results from the fact that the lever 100 is just below a horizontal position for zero compressor pressure and sloping down toward the right at other values of compressor pressure. Under such conditions movement of'rod 106 to the left will cause the throttle valve to move toward a closed position. In the event that an underspeed condition exists, the flyweights of the governor will move the pilot valve 182 t to the right thereby directing drain pressure through the line 188 and eventually to the line 196 in the chamber 198 so that the high pressure on the left-hand side of the main servo piston 110 will move the piston to the right to increase its effect on the multiplying linkage and thus to move the valve for increased fuel ow. It will be noted that the speed governor 180 includes a spring 200 which has an operative connection via the lever 202 to the main servo piston 110. Thus, each movement of the servo piston 110 causes a resetting of the governor 180 thereby providing a. permanent droop in the response of this governor. A second spring 204 is adjusted via a cam schematically illustrated at 206 which is moved in response to movements of the pilots lever 208. Hence, different power settings will correspond to different speed settings of the speed governor 180. With a droop governor of the type shown a signal is obtained which levels out at a predetermined high speed to establish in the throttle valve a minimum fuel liow which is proportional to compressor pressure.

It will be noted that the pilot valve 182 controlled by the speed governor 180 is capable of controlling the main servo piston 110 only when the valve 192 is positioned as shown in Fig. 2. The pilot valve 192 acts as an overriding mechanism which responds to a function of excessive temperature at the compressor inlet and the speed of the power plant. The valve 192 then is a maximum limiting valve. Motion is imparted to the movable member 220 of the valve 192 by means of a lever 222 and a knife edge 224. Motion is imparted to the knife edge 224 by a three dimensional cam 226 which rotates in response to compressor inlet temperature and reciprocates in response to power plant speed. The operational ,movements of the cam in response to these parameters will be described hereinafter. However, when the desired limits are reached the knife edge 224 is moved to the right as is the central valve element 220 of the valve 192. This motion of the valve element 220 places the line 196 in communication with the high pressure fuel line 230 so that high pressure fuel exists in the chamber 198 on the right-hand side of the servo piston 110 to cause a corresponding decrease in fuel ow.

It shouldbe added that the minimum opening of the throttle valve 70 is set by an adjusting screw 212 which engages the right hand end of the main servo piston 110 to limit the pistons leftward movement.

In order to obtain rotation of the three dimensional cam 226 in response to compressor inlet temperature, a bulb 250 is provided which communicates with bellows 252. Variations in pressure within these bellows causes motion through a rack and pinion 256 which in turn moves` a pivoted arm 258. The bellows 254 acts as a compensating bellows while the bellows 252 is the temperature responsive bellows. The compensating bellows 254 is connected to line 253 which is closed at its terminous adjacent the temperature sensing bulb. Hence Vany variations inV temperature which may occur along the lines between the sensing bulb and the bellows will be compensated for at thel bellows. In other words, any variations occurring between the sensing bulb and bellows 252 will Ybe counteracted by similar but opposing action by bellows 254 on pinion 256. Motion of the arm 258 moves the valve element 260 so that downward motion of the valve will connect the chamber 262 with drain pressure then existing in the chamber 264. Upward motion of the valve 2 60 connects the chamber 262 with the high'pressure chamber 266. .With high pressureinnthe chamber V262 themain servo body.268iwill lbemoved lupwardly so as to impart motion to the rack'and pinion 270 and also the gears 272, 274. The gear 2742is splined at 276 with the main cam-body so as to rotate the cam in a given direction. When drain pressure exists 1n the Vchamber 262 the high pressure in the chamber 266 forces the servo main body 268 in a downward direction to rotate the three dimensional cam 226 in the opposite direction.

The three dimensional cam 226 is reciprocated by means of a-speed responsive servo system which provides a permanent droop inthe governing action of the system. A speed governor 290 is driven by aV drive shaft 292 and acts to reciprocate a pilot valve 294. The pilot valve 294 permits communication of high pressure from the line 296 or drain pressure from the line 298 into the line 300 which leads to the upper chamber 302 and the lower chamber 304 at opposite ends of the pilot valve. This insures equal force on either end of the pilot valve. However, at the same time the cam 226 is forced in either of two directions depending on whether drain pressure or high pressure is being admitted to the chamher 302 adjacent the lower end of the cam body. It will be noted that with each axial movement of the cam 226 the tension on spring 310 will be varied so that in reality the speed governor 290 will be reset. This provides a servo mechanism in which the cam 226 will have a definite position for each speed setting of the governor.

The surface contour of the cam 226 is determinedby superimposing a family of curves corresponding to the compressor surge line and maximum desirable temperature. The curves in the nal analysis are plotted as a comparison of the ratio of fuel flow and compressor pressure against engine speed. The family of curves `is obtained by plottingthem for various values of inlet temperature. The surge line and maximum desired'temperature together then define the cam contour. The'theoretical derivation of these curves is omitted herein for convenience. It should be added that compressor surge is that point at which under particular conditions the cornpressor operates `erratically.

From the foregoing description it is evident that the major controlling parameters are that of engine speed and compressor pressure. Signals equivalent to these parameters are multiplied for controlling a single throttle valve. The speed controlling signal is subject to being oveiriden by a maximum limiting signal corresponding to speed and compressor inlet temperature. The cornpressor pressure signal is subject to being modified or limited in its controlling eect by the reversing mechanism in the compressor pressure servo system 134.

The governor 180 of Fig. 2 andits related system may include a temperature compensating :device which is schematically illustrated in Fig. 5. Thus a speed governor 18% is shown including a reset spring 330 which is varied in tension upon movement ofalever 332 about its pivot 334. The main servo which feedsmotion to the-multiplying mechanism at the throttle valve tends to reset the governor for each position thereof. For variations in ambient air temperature certain compensation may be desired either to maintain the power plant speed constarrt at given power settings or to vary speed according to a desired schedule while operating through varied ambient air temperatures. To this end a cam 336 .may be utilized to vary the position of the pivot 334 in response to variations in ambient air temperature. The particular type of desired response will be determined by the prole of cam 336.

In addition, it may be desirable to avoid apermanent droop effect in the governor` 180 of Fig. 2 and its related system. To obtain this eect a dashpot may be provided to produce a temporary feedback to the reset spring upon movement et the main servo. This additional'feature is best-lshownfin-Fig.`-6. `Herethe governor v'liras a setting spring and a Vpreload `spring 342. The'pivot point 344 has a dashpot connected thereto, as illustrated. Thus, movements of the main servo will have only a temporary eiect on the `setting of the governor and providesisochronous governing action.

AReferring to Fig. 4, a turbo-prop version of the fuel control of this invention is illustrated. The Fig. 4 fuel system is substantially identical to that illustrated in Fig. 2 with a few structural elements added thereto. Hence, in describing Fig. 4, repetition of the operation of several major components will be omitted for convenience.

Thus the throttle valve is -identical to the Fig. 2 construction and is operated in substantially the same manner. The compressor pressure servo system 134a moves its knife edge 102 to'increase fuel flow proportional to compressor pressure. Though not shown herein, a system identical to 134 of Fig. 2 maybe usedso that the servo system operates to move the knifeedge to increase fuel in response to pressure increase vup to -a predetermined pressure and then to decrease fuelflow with further increase in compressorpressure. The servo system 134a operates to move knife edge 102 in response to movements of valve 320 which directs either high or low pressure fuel to the chamber 322 above the main servo body 324. Motion of the knife edge 102 is multiplied by the motion of the main servo piston 110. In the case of this constructiomhowever, the speed governor 1800 is utilized as an underspeed governor rather than as a primary controlling unit.

The normal or primarycontrol utilizes a function of compressor inlet temperature and power plant speed With theresultant motion produced by the temperature sensing servo. and the speed governor` 290@ on the three dimensional cam 226g. Thus the cam 226:1 includesa normal control cam surface,.a maximum limit cam .surface and an overspeed cam surface as labeled inFig. 4. With the temperature sensing servo and the speed governor 290a, including its servo system, operating in the mannerdescribed in connection with Fig. 2, thek normal control cam portion of the cam 226a operates a member 410 which imparts motion to a lever 412 via a roller 414. The roller 414 varies the fulcrum between the member 410 and the lever 412 by being reciprocated by a'rod 416. Rod 416 is in turn operated through abell crank 418 which has an operative connection to the pilots lever 208. The output of the lever 412 is in reality equal to the product of the motion resulting from the speed and temperature function and the motion of the roller 414 as caused by movement of the pilots lever 208. As dirliering now from the control illustrated in Fig. 2, the output ofthe lever 412 is imparted to the movable portion 422 of a normal control pilot valve 424 which is interposed in series between the pilot valve 182a of the speed governor g and the maximum limit 'pilot valve 192.

Since the speed governor :1 functions as an underspeed governor it will have a. setting somewhat lower than the propeller governor illustrated in Fig. l. Then, as .far as the governor o is concerned, the power plant in the normal range of operation is continuously overspeedmg to the extent that high pressure iluid will be directed Vinto the line 188e which leads to the normal control pilot valve 424. The normal control pilot valve 424 can permit this high pressure flow to enter the yline 428 leading to the maximum limit pilot valve 192 or else 1t can admit drain or low pressure iluid viarthe line 430 to the line 42S leading to the maximum limit valve 192. in the normal control range then the pilot vvalve 182a of the speed governor 180g and the maximum limit pilot valve 192 are notl effective to control the flow of'uid leading tothe-main Vservo via the line 196a.

yAs previously described, the'maximum limit pilot valve .iwan-response to excessive-temperature or speed can f zgeszgeee permit high pressure fluid to'llow from Vthe line 298a into the line 196e to move the main servo piston 110 to the left to decrease fuel flow.

-As stated above, the propeller governor will have a higher speed setting than the underspeed governor 180a to the extent that the propeller governor will, for example, be set to move the propeller blades lagainst their low pitch stop, for instance below 1000 R. P. M. The underspeed governor 180o on the other hand as a result of the tension of its springs and the contour of the cam 206a, will be set to take effect for example at 950 R. P. M. Thus at power plant speeds below 1000 R. P. M., as for example when the power plant is throttled back in landing approach of the aircraft, the normal control pilot valve will be positioned so as to permit communication of fluid from the pilot valve 182e via the line 18%(1 down through the maximum limit pilot valve 192 and eventually to the main servo and its piston 110. The normal control pilot valve 424 is positioned in this manner in low power settings of the pilots lever 298 since the bell crank 418, rod 416 and roller i4 will be positioned to move the lever 412 and the movable element 422 of the pilot valve 424 to the right to open the line 428 to line 188:1

. leading from the pilot valve 182e.

In a turbo-prop installation and particularly in multiengine operation, having an underspeed governor is of primary inportance. At low power settings and low or zero thrust, a turbo power plant is developing and consuming power in the turbine (to drive the compressor) at a relatively high rate. Therefore, small variations in fuel ow in this range can result in rapid and large changes in positive or negative thrust output. In a multi-engine installation considerable yaw in the aircraft would normally be experienced. The underspeed governor then accurately controls power plant speed and thrust by regulating fuel ow in this power range setting to overcome sudden variations in thrust.

rAnother reason it is desired to have the underspeed governor control power plant speed in the low prop R. P. M. range is that in the event ya go-around is necessary, immediate response of the power plant is desired. Since the inertia of a gas turbine power plant is relatively high, it is desirable to maintain its speed relatively high in the low power settings. Thus: the underspeed governor maintains a relatively high power plant speed bypdirectly controlling fuel ow in multiplied relation with compressor pressure where the propeller blades of a turboprop installation are against their low pitch stop and the pilots lever is at a low power setting other than in the -idle or off position, for example, in a ight idle position. The underspeed governor also controls the ground idle of the power plant.

It is, of course, apparent that the idle or minimum flow setting for the throttle valve 70 is preset by the adjusting mechanism 2l2a as in the case of the fuel sys- 1 tern illustrated in Fig. 2.

It will be evident that as a result of this invention an accurate, highly responsive but rugged fuel control has been provided which is adaptable to various types of gas turbine power plants.

p compressor, a combustion section and a turbine for driving the compressor, a source of fuel under pressure, means for injecting fuel into said combustion section including a throttle valve between said source and said combustion section, a lirst means movable in response to compressor pressure, a second means movable in response to the speed of rotation of said power plant, means operatively connected to said throttle valve and said rst and second means for 'multiplying the movements of said rst and second' means and varying the'opening of said throttle valve i'n proportion to the product of said movements, and means responsive to speed and another' parameter of power plant operation and operatively connected to said throttle valve for limiting the throttle valve opening.

2. In a fuel control for a turbo power plant comprising a compressor, a combustion section and a turbine for driving the compressor, a source of fuel under pressure, means for injecting fuel into said combustion section including a throttle valve between said source and said combustion section, means for maintaining a constant pressure drop across said throttle valve so that a certain throttle valve opening provides a predetermined llow, a first means movable in response to compressor pressure, a second means movable in response to the speed of rotation of said power plant, adjustable means for modifying the response of said second means, means operatively connected to said throttle valve for multiplying `the movements of said lirst and second means and varying the opening of said throttle valve in proportion to the product of said movements, and means responsive to at least two parameters of power plant operation and operatively connected to said throttle valve for limiting the throttle valve opening.

3. In a fuel control according to claim 2 wherein said last mentioned means includes operative connections to said multiplying means and includes means for overriding said second means.

4. In a fuel control for a turbo power plant having a compressor, a combustion section and a turbine for driving the compressor, a source of fuel under pressure, means for injecting fuel into said combustion section including a throttle valve between said source and said combustion section, means for maintaining a constant pressure drop across said throttle valve so that aV certain throttle setting provides a predetermined liow, a first means movable in response to compressor pressure, a second means movable in response to the speed of rotation of said power plant, adjustable means for modifying the response of said second means, means operatively connected to said throttle valve for multiplying the movements of said rst and second means and varying the opening of said throttle valve in proportion to the product of said movements, and means including a servo device responsive to compressor temperature land another parameter of power plant operation in mixed relation and operatively connected to said multiplying means for limiting the throttle valve opening in proportion to compressor pressure.

Y provide a controlling signal 5. A fuel control according to claim 4 wherein said servo device includes a three dimensional cam movable in one direction in response to engine speed and in another direction in response to compressor temperature to for limiting throttle valve opening.

6. In a fuel control for a turbo power plant, the power plant comprising a compressor, a combustion section and a turbine, a source of fuel under pressure, means for iniecting fuel into said combustion section including a throttle valvebetween said source and said combustion section, means for maintaining a constant pressure drop Ymovements of said speed responsive means, adjustable Vmeans for varying the response of said speed responsive at apredetermned point in :thepower plan-tv for limiting .means and'fmodiying thefoutput oftfsadlniultiplyingade- `:vi'ce,landt-means 'responsiveto 'at fleast`twoiparameters of power V.plant .operation and operatively connected to said throttle valve forlimitingthe throttle valve opening.

7. .In a fuel control Vfor a turbo power plant, the powerplant comprising a compressor, a combustion section and a turbine for driving the compressona source -offuel under pressure, means for delivering fuel from said source to said combustion section including a throttle valve,uand means responsive to two parameters of power plant operation is mixed relation for'varying the opening of said valve including operative connections to said valve, said last'mentioned means-including-mechanism movable-in onev direction in responseto variation in one of saidiparameters -up to a predetermined value and movsable in a reverse direction upon'said one parameter varying beyond said predetermined-value.

8. In a fuel control for aturbo powerk plant having a compressor, a combustionsectionand .a turbineV for driving the compressor, a source of fuel under pressure,'means for-'delivering fuel from :said source-to-.said combustion -section including a throttlevalve,- means-for. maintaining va first signal to be multiplied -tosaidmultiplying-device including operative connections thereto, means responsive rto a function of speed of the power plant-and .the temperavture vat a predetermined point inthe power plant for transmittingasecond signal to be multiplied to saidmult-iplying `device including operative connections `thereto, and means responsive to a function of-fspeed and temperature compressor surge and temperature of the -power plant.

9. In a-fuel control accordingto-claim 8 .including speed responsive means operatively connected towsaid multiplying .device for transmitting a third signal tosaid multiplying means below.apredetermined.speedlof the power plant.

-l0.`In a fuel control according'to claim 9 including means responsive to a function of speed .and temperature and operatively connected-to said multiplying device for transmitting aV fourth signal thereto, said.` last mentioned means including mechanism for disabling vthe means transmitting said second and third signals to said device.

l1. In a lel control for a turbo powerj plant having a compressor, a combustion section and a turbine for driving the compressor, a source of fuel underpressure, means for deliveringV fuel from Vsaid source to said combustion section including .a throttle valve, means for `mgaintaining a constant pressuredrop across the throttle valve so that a certain valve position providesa predetermined flow, a multiplying device Voperatively connected to said throttle' valve for positioning the valve and 'metering the fuel flow,*means responsiveto compressor pressure for transmitting 'a'first signal'tobernultiplied to said multiplying device including operativeconnections thereto, 'means responsive to'speed "of' the power plant'for transmitting a second signal to be multiplied to saidrnltiplying device including' operative connections thereto, and means for limiting the flow of fuel comprising'neans for Vmodifying saidsecond signal, said lastmention'ed means including mechanism responsive to a'functicn of speed of the power plant and temperature at a'selected point in the power plant. y

l2. In a fuel control according to'claim 1l"`wherein thev first signal is generated by a mechanism producing a signal falling oif above a predetermined 'compressorpressure `to reduce fuel flow' andV establishing a 'maximum'compressor pressure limit.

13. In4 a fuel control according toclaim llwher'einY the second signal is producedfby-afdroop governor comprising mechanism which-produces a `signal -levelingout at -al'pr'edetermined high '..speed tofestablish afminimum '.ifuel flow :limit which :Pis proportional ,to compressor .pressure zl4..lIn.a fuel control'according .to claim 1'2 wherein the second'signal is generated byla droop governor com- :prising mechanism which .produces a signal levelingout at apredeterminedzhigh speed to establish a minimum fuel 'ow 'limit which.isfproportional-to compressor pressure.

15. vIn a fuelacontrolaccording to .claim l2 wherein themechanism; producing said rst signal comprises a movable output member vhaving two sides, means for continuously exposing one Vof said sides to fuel under high pressure from said source,l a source of fuel under l-owpressure, Vvalvemeans movable in one direction for controlling the flow lof high pressure fuel to theother side of said` member to move said member inAsaid one direction, and means operatively connected to said valve means 'for admitting low pressure fuel to the other'side of saidmember .to-move said member .in another direction upon continued movement of said -valve in said one direction beyond a predetermined*v point.

16. In a fuel control for a turbo power plant, the

powerplant comprising-a compressor, a -combustion section and a turbine, a source of fuel under pressure, means for-injecting fuel into said lcombustion section including .a throttle valve between said source and said combustion section, means for maintaining a constant pressure drop across said throttle valve so 'that a certain throttlevalve opening .provides a predetermined flow,y av multiplying device operatively connected to said throttle valve for varying the opening thereof, means movable in response to compressor pressure yoperatively connected to said multiplying device for feeding thereto a signal to be multiplied, 'means movable in response to the speed of rotation ofthe power plant, a servomotor operatively connected to said-device for feeding thereto a signal to be mul'tipliedysaid` servomotor including a, pilotvalve controlled by movements of said speed responsive means, adjustable means for-varying the response of -said speed responsivemeans and modifying the output of said multi- ,'plyingdevice, arsecond means movable in response to the `speed of rotation of saidpower plant, means movable in response tothe temperature at a preselected point in said power ,--plant, and meansfor mixing the movements of said second means and said temperature responsive means for producing a. resultant signal, a second pilot valve for yre'ceivingfsaid resultant signal-and operatively connected `mined compressor pressure.

18. In-a fuel control for a turbo. power plant, the power .plant comprising a compressor, a combustion section and a turbine, a source lof fuel under pressure, means for injecting. fuel into said combustion section including a Ythrottle valvey between said source and said combustion section, means for maintaining a constant pressure drop across said throttle valve sothat a certain throttle valve opening provides a predetermined ow, a multiplying deviceeoperatively connectedV to said throttle valve for varying the opening thereof,tmeans `movable in response to `compressorpressure operatively connected to said multi- Vplying device. for Yfeeding thereto .a signal to be multigplied, means movable .in response to the speed of rotation ofthe power plant, a servomotor operatively connected to said device for feeding thereto a signal to. be multiplied, said scrvomotorincluding a pilot valve controlledby movements of said speed responsive means, ad-

justa'ble means .forvarying Athe response of said speed re- `sponsive means.' .and modifyingthe output of said multi- Y:plyingdevice,..a camfmovable in Alinear directions .and

transversely of said linear directions, a second means movable in response to the speed of rotation of said power plant vincluding a servo system for moving said cam in one of said directions, means responsive to the temperature at a preselected point in said power plant including a servo system for moving said cam in another of said directions, the motions of said cam producing a resultant' signal, a second pilot valve for receiving said resultant signal and operatively connected in series with said first mentioned pilot valve and said servomotor for modifying the effect of said first mentioned pilot valve on said first mentioned servomotor.

19. In a fuel control according to claim 18 including adjustable means operatively connected to said first mentioned servomotor for limiting the effect of said rst mentioned servomotor on said device and throttle valve.

20. In a fuel control according to claim 19 including means operatively connecting said cam to said second speed responsive means for varying the response thereof upon repositioning of said cam in its motion in said one direction.

`2l. In a fuel control for a turbo power plant, the power plant comprising a compressor, a combustion section and a turbine, a source of fuel under pressure, means for injecting fuel into said combustion section including a throttle valve between said source and said combustion section, means for maintaining a constant pressure drop across said throttle valve so that a certain throttle valve opening provides a predetermined flow, a multiplying device operatively connected to said throttle valve for varying the opening thereof, means movable in response to compressor pressure operatively connected to said multiplying device for feeding thereto a signal to be multiplied, said pressure responsive means including a movable member and a servo mechanism for moving said member in one direction as a linear function of compressor pressure and moving said member in the opposite direction upon an increase in pressure beyond a predetermined value, means movable in response to the speed of rotation of the power plant, a servomotor operatively connected to said device for feeding thereto a Y signal to be multiplied, said servomotor including a pilot valve controlled by movements of said speed responsive means, adjustable means for varying `the response of said speed responsive means and modifying the output of said multiplying device, a cam movable in linear directions and transversely of said linear directions, a second means movable in response to the speed of rotation of said power plant including a servo system for moving said cam in one of said directions, means responsive to the temperature at a preselected point in said power plant including a servo system for moving said cam in another of said directions, the motions of said cam producing a resultant signal, a second pilot valve for Areceiving said resultant signal and operatively connected in series ,with

said first lmentioned pilot valve and said servomotor for modifying the effect of said first mentioned pilot valve on said first mentioned servomotor.

22. in a fuel control for a turbo power plant, the

power plant comprising a compressor, a combustion section and a turbine, a source of fuel under pressure, means for injecting fuel into said combustion section including a throttle valve between said source and said combusplying device operatively connected to said throttle valve for varying the opening thereof, means movable in respouse to compressor pressure operatively connected to said multiplying device for feeding thereto a signal to be multiplied, said pressure responsive means including a movable member and a servo mechanism for moving said member, a cam movable in two directions including f a cam' surface-means movable in response to the speed of rotationof--said power plant including a servo system for moving v'said cam in one of said directions, means responsive to the temperature at a preselected pointY in the power plant including a servo system for moving said cam in another of said directions, a cam follower cooperating with said cam surface for producing a second signal, means for producing a third signal, means for multiplying said second and third signals, a servomotor operatively connected to said multiplying device for feeding thereto a signal to be multiplied, and a pilot valve operatively connected to said multiplying means and controlling said servomotor. Y

23. In a fuel control for a turbo power plant, lthe power plant comprising a compressor, a combustion section and a turbine, a source of fuel under pressure, means for injecting fuel into said combustion section including a throttle valve between said source and said combustion section, means for maintaining a constant pressure drop across said throttle valve so that a certain throttle valve opening provides a predetermined ow, a multiplying device operatively connected to said throttle valve for varying the opening thereof, means movable in response to compressor pressure operatively connected to said multiplying device for feeding thereto a signal-to a be multiplied, said pressure responsive means including a movable member and a servo mechanism for moving said member, a cam movable in two directions including at least two cam surfaces, means movable in response to the speed of rotation of said power plant including a servo system for moving said cam in one of said directions, means responsive to the temperature at a preselected point in the power plant including a servo system for moving said cam in another of said directions, a cam follower cooperating with one of said cam surfaces for producing a second signal, means for producing a third signal, means for multiplying said second and third signals, a servomotor operatively connected to said multiplying device for feeding thereto a signal to be multiplied, and a pilot valve operatively connected to said multiplying means and controlling said servomotor, a second cam follower cooperating with the other of said cam surfacespand a pilot valve operatively connected to said second cam follower including operative connections to said servomotor and said first mentioned pilot valve for overriding the effect of said first mentioned pilot valve on said servomotor. t

24. In a fuel control according to claim 23, including a second speed responsive means having a third pilot valve operatively connected to said pilot valves and said servomotor.

25. In a fuel control for a turbo power plant having a compressor, a combustion section and a turbine driving the compressor, a source of fuel under pressure, means for delivering fuel from said source to said combustion section including a throttle valve, said throttle valve including a movable element for varying the opening of said valve, means responsive to compressor pressure including a first member movable in one plane, a member pivoted at one end to fixed structure and having its free end engaging said first movable member, said pivoted member being located adjacent to said movable valve element, means responsive to the speed of the power plant including a first pilot valve movable thereby, a servomotor controlled, by said first pilot valve including a member interposed between said-movable valve element and said pivoted member, said servomotor member being movable transversely of said first movable member vwhereby the-,movements of said first movable member and said servomotor member are multiplied to move said valve element, a second pivoted member having operative connections with said servomotor and said speed responsive means for resetting the latter upon movement of said servomotor, a second pilot valve operatively connected in series with said rst pilot valve and between said rst valve and said servomotor, said second valve including a'p'ivot and a lever carried by said pivot, one

free end of said lever having an operative Icoiiiiectic'n to said servomotor, a followeropeatively'engaging'the other free end of said lever. a three Vdime`nsional-`cam 'engaging said follower, a spee'dresponsive device including a servo system for moving said cam in one direction and including mechanism for `varying'tlie response of said device upon movement of said cam, an'd1atem perature responsive device including a servo system for moving said ca m in another direction.

26. In a fuel control according to claim 25 including a second temperature responsive device operatively connected to the pivot of said second pivoted member for varying the position of the pivot. A

27. in a fuel control according to claim 25`including a spring for' setting said speed responsive means, a second lspring for preloading said first spring,'and means operatively connected to the pivot of said second pivoted mem- VVber for temporarily resetting said speed responsive means to provide for temporary droop operation of'said speed responsive means. v

28. In a fuel control according toclaim 27 wherein said means for temporarilyv resetting the speedresponsive means comprises a dashpot'mechanism.

29. In a fuel control for a turbo power plant having a compressor, a combustion section anda turbine driving the compresson'a source of'fuelunder pressure, means for delivering the'fuel from said source to said combustion section including a throttle valve, said throttle valve including a movable elementfor'varying the opening of said valve, means responsive to compressor pressure including a first member movable'in one plane, a member pivoted at one end to fixed structure and having its free end engaging saidrst movable member, said pivoted member being located adjacent'to `said movable valve element, means responsive tothe speed of the power plant including a rstpilot valve mov-able thereby, a servomotor controlled by said -iirst pilot-valve including a member interposedbetween Ysaid movable valve element and said pivoted member, said servomotor member being movable transversely of said rstmovable member whereby the movements ofsaid first 'movable member and said servomotor member aremultiplied to move said valve element, asecond pivoted'memberhaving operative connections with said servomotor and said speed responsive means for resetting the latter upon movement of said servomotor, a second pilot valve operatively connected in series with said iirst'pilot valve and between said first valve and said servomotor, said second valve including a pivot and a lever carried by said pivot, one free end of said lever having an operative connection to said servomotor, a rst follower operatively engaging the other yfree end of said lever, a three dimensional cam having at least two camsurfaces, one of said surfaces engaging said follower, a speed responsive device including a servo system for moving-said cam linearly, a temperature responsive Idevice including a servo system for moving said cam transversely of said linear movement, a second cam follower engaging the other of said cam surfaces, a second lever having a pivot intermediate its ends, one end of said second lever being located adjacent said second cam follower and the other end of second lever being operatively connected to said servomotor, a member interposed between said second cam follower and said one end of said second lever, means for moving said last mentioned member transversely of the following movements of said second cam follower, and a'third pilot Vvalve operatively connected to the pivot of said second lever, said third valve being operatively connected inseries-between said second pilot valve and said servomotor.

l30. In a fuel control for a turbo power plant comprisving a compressor, a combustion section and a turbine, a

source of fuel under pressure, means for injecting fuel into said combustion section including a throttle valve between said source `and said Vcombustion nsection, said throttle valve including a movablefelement having a l's'urfa'ce thereon, means for-maintaining a constant pressure-"dcrp-a "oss said throttle valve so that a certain-throttlevalve opening provides a predetermined'ow, meansiresponsiveto compressor pressure includinga first-movable 'tnember, :an arm pivoted at one end andengaginglsaidmovable member at a point intermediateth'e endsof-isaid anmnieans responsive to the speed of the fpowe'r 'fplant including =a second member movabletransversely ofisaidfirstrmovable member and engaging said arm andi said surfacelwhereby the movements of said members aremul'tipliedtornove said movable elementofthe valve. g

3l. In a fuel controlaccording to clainiwherein'said means responsive to compressor-"pfessureincludes` aiservo system for moving saidiirstmovablemember andlfsaid speed responsive means* includes fa :servo 's'ys'temt-for-'rnoving said second member.

32. In afuel control accordingto claim `3l wherein said servo systems -areoperated byfuelvfromsaidsource.

33. In ia fuel control iaccordingto'fclaim 4 v'wherein said servo device comprises aluidcylindeL-asource'of fluid under 'pressure, means Yfor controlling tlie'flow Aof fluid to cylinder-including aplui'alityof pilotvalves-in series relation between said?sourceCandi'cylinder,lone"'of said valves beingres'ponsive t'o apower plant 'operating temperature and anotherparameter of engine operation, and means for overriding the effectrof one -of'said valves on saidcylinder upon movement-ofanotherlof saidfvalves in a given direction.

34. In a fuel control'according to'cla'im 33 'wherein'said servo device includes at least-611e ladditionalpilot valve in series with said plurality VVof valves, and fmeans for overriding the Veffect of said plurality ofvalves'on said cylinder upon movement of said additional valvein a'given direction.

35. In a fuel control for a turbo powerplant having la compressor, a combustion section and! al' turbine' for 'driving the compressor, v a source of fuel under pressure, means for delivering fuel from sai'dsource 'to said-cotnbustion section including athrottle valve, amultiplying device operatively connected to saidVL throttle fvalve'for positioning the valve and meteringthe fuelw'owf-means responsive to compressor pre'ssure'for"transmittinga'fiirst signal to be multiplied to said multiplying device including operative connections theerto, means responsive to a function of a speed of the power plant and the temperature at a predetermined point in the power plant for transmitting a secondsignal to be multiplied to said multiplying-device including operative connections thereto, and speed responsive' means 'operatively connected to saidmultiplying de- `vice for transmitting Ia thirdsignal to said multiplying means below a predetermined speed of the'powerV plant.

36.'Ina fuel :control for a'tu'rbo'powerplant having a compressona combustion section and a turbine for driving the compressor, a source of fuel under pressure, Imeans for delivering fuel from said source to said combustion section including a throttle valve, a multiplying device voperatively connected to said throttle-valve for'positioning the valve and metering ther fuelhow,'means responsive to compressor pressure for Itransmitting'anrstsignal to be multiplied to'said multiplying device including operative connections'thereto, means responsive to a functiony of speed of the power plant for transmitting a second signal Y to be multiplied `to said multiplying device including operative connections thereto, and means responsive to'a function ofspeed |and temperature atY a predetermined point in' `the rpower plant for 'modifying at least one of said signals. f

37. In a fuel control fori-a' tur-bo power plant having a compressor, a :combustion section and a turbine for driving the compressor, a source of 'fuel under pressure, means for delivering fuel fromk said source to said combustion "section including va throttle valve mechanism, a lmultiplying device operatively connected to said'throttle valve mechanism for positioningthe valve and metering the fuel ow, means responsive to compressor pressure'for transmitting a first signal to be multiplied to said multiplying device including operative connections thereto, and means responsive to la function of speed of the power plant for transmitting a second signal to be multiplied to said multiplying device including operative connections thereto, said last mentioned means including a droop governor, said governor including mechanism which produces a signal leveling out at a predetermined high speed to establish a minimum fuel flow which is` proportional to compressor pressure.

38. In a fuel control for a power plant having a rotating member, a source of fuel under pressure, means for conducting fuel from said source to said power plant including mechanism for controlling the amount of fuel ow, means responsive to the speed of rotation of said power plant, means responsive to 'an operating pressure of the power plant, means responsive to an operative temperature of the power plant, means operatively connecting said speed responsive means and said pressure responsive means to said controlling mechanism for regulating fuel ow during steady state operation of the power plant as a function of the product of said speed and pressure, and means operatively connected to each of said responsive meons and said controlling mechanism for regulating fuel ow proportionately to the product of pressure and a function of speed and temperature.

39. In a fuel control for 'a power plant having a compressor, a combustion section and means for driving the compressor, a source of fuel under pressure, means for conducting fuel from said source into said combustion section including mechanism for controlling the amount of fuel ow, means responsive to the speed of rotation of said 'power plant, means responsive to an operating pressure of the power plant, means responsive to an oper-ative temperature of the power plant, means operatively connecting said speed responsive means and said pressure responsive means to said controlling mechanism for regulating fuel iiow during steady state operation of the power plant as a function of the product of said speed and pressure, and means operatively connected to each of said responsive means and said controlling mechanism for regulating fuel flow proportionately to the product of pressure and a function of speed and temperature, and means operatively connected to said pressure responsive mechanism and said compressor for limiting the compressor discharge pressure.

40. In a fuel control for a turbo power plant having a compressor, a combustion section and a turbine, a source of fuelunder pressure, means for controlling Vthe flow of fuel from said Vsource to said combustion chamber including a signal combining device, means responsive to a parameter of power plant operation for transmitting a first signal to said device, speed responsive means for transmitting a second signal to said device including a speed governor, means for setting the speed at which the governor will govern, and means responsive to at least one parameter of power plant operation for changing said speed setting in accordance with variations of said one parameter.V

4l. ln a fuel control for a turbo power plant having a compressor, a source of fuel under pressure, means for injecting fuel into Vsaid combustion section including throttle valve mechanism and having a multiplying device controlling the amount of fuel flowing to said combustion section, a tirst means movable in response to a parameter of power plant operation and operatively connected toV said multiplying device, and a second means responsive to compressor pressure operatively connected to said multiplying device and including mechanism for increasing the ow of fuel with an increase in compressor pressure to a predetermined value and decreasing fuel ,dow with further increase in compressor pressure beyond said predeterminedvalue. Y y i 42,. ln a fuel control for a turbo power plant having Cil a compressor, a combustion section and a turbine, a source of fuel under pressure, means for controlling the iiow'of fuel from said source to said combustion chamber, means providing a signal repsonsive to the speed of the power plant, Ameans providing a signal responsive to temperature at the inlet to the power plant, means providing a signal responsive to the discharge pressure of said compressor, `and means for transmitting said signals to said fuel control means whereby the fuel dow is regulated as a function of the product of the speed and compressor pressure signals during steady state operation and as a function of the pressure signal multiplied by the combined speed and temperature signals during maximum acceleration.

43. In a fuel control for a turbo power plant comprising a compressor, a combustion section and a turbine, a source of fuel under pressure,lthrottle valve means for controlling the flow of fuel from said source to said combustion chamber including two movable members, means responsive to the movement of said movable members for multiplying the movements thereof, means movable in response to compressor pressure operatively connected to one ofY said movable members, means movable in response to the speed of the power plant including a servo system operatively connected to the other of said movablemembers, said servo system comprising a iluid cylinder, a source of iluid under pressure, means for controlling the Vflow of fluid to said cylinder including a plurality of pilot valves in series relation between said source and said cylinder, one of said valves being responsive to two parameters of power plant operation, and means for overriding the effect of one of said valves on said cylinder upon movement of another of said valves in a given direction.

44. In a fuel control for a turbo power plant, the power plant comprising a compressor, a combustion section and a turbine, a source of fuel under pressure, means for controlling the flow of fuel from said source to said combustion section including a multiplying device, means movable in response to compressor pressure operatively connected to said multiplying device for feeding thereto a signal to be multiplied, means movable in response to the speed of rotation of the power plant and operatively connected to said multiplying device for feeding thereto a second signal to be multiplied, adjustable means for varying the response of said speed responsive device and modifying the output of said mutiplying device, a cam movable in linear directions and transverselyof saidv linear directions, a second means responsive to the speed of rotation of the power plant for moving said cam in one of said directions, means responsive to the temperature at a preselected Vpoint in said power plant for moving said cam in another of said directions, the motions of said cam producing a resultant signal, and means receiving said resultant signal for modifying the effect of said second signal. Y

45. In a fuel control for a turbo power plant having a compressor, a combustion section and a turbine for driving the compressor, a source of fuel under pressure, means for delivering fuel from said source to said combustion section including a throttle valve, means for maintaining a constant pressure drop across the throttle valve so that a certain valve position provides a predetermined ow, a multiplying device operatively connected to said throttle valve for positioningthe valve and metering the fuel flow, means responsive to compressor pressure for transmitting a iirst signal to beV multiplied to said multiplying device including operative connections thereto, means responsiveto a function of speed of the power plant 'and the temperature at a Apredetermined point in the power plant for transmitting a second signal to be multiplied to said multiplying device including operative connections thereto, means responsive to a function of speed and temperature at a predetermined point in the power plant for limiting compressor surge and temperature of the power plant including operative connectionsv to said multiplying device, and manually operated means for modifying the operation of said last mentioned means.

46. In a fuel control according to claim 25 including mechanism responsive to at least one parameter of power plant operation operatively connected to the pivot of said second pivoted member for varying the position of the pivot.

47. In a fuel control for a turbo power plant having a compressor, a combustion section and a turbine for driving the compressor, a source of fuel under pressure, means for delivering fuel from said source to said combustion section including a multiplying device for metering the fuel ilow, means responsive to compressor pressure for transmitting a first signal to be multiplied to said multiplying device including operative connections thereto, means responsive to speed of the power plant for transmitting a second signal to be multiplied to said multiplying device including operative connections thereto, and means for limiting the flow ofV fuel comprising means for modifying said second signal, said last mentioned means including mechanism responsive toa function of speed of the power plant and temperature at a selected point in the power plant.

48. In a fuel control for a turbo power plant having a compressor, a combustion section and a turbine for driving the compressor, a source of fuel under pressure, means for delivering fuel from said source to said combustion section including a multiplying device for metering the fuel ilow, means responsive to compressor pressure for transmitting a rst signal to be multiplied to said multiplying device including operative connections thereto, means responsive to speed of the power plant for transmitting a second signal to be multiplied to said multiplying device including operative connections thereto, and means for limiting the ow of fuel comprising cam means for modifying said second signal, said last mentioned means including mechanism movable in two directions in response to a function of speed of the power plant and temperature at a selected point in the power p ant.

49. In a turbine type power plant, a source of fuel under pressure, valve means for regulating the ow of fuel to the power plant, a power setting lever, normal control means operatively connected to said valve means for metering fuel flow as a function of a power plant pressure signal, a function of the setting of said lever and a function of a power plant temperature, maximum limiting means operatively connected to said valve means for limiting fuel ow as a function of a power plant pressure signal, a function of speed and a function of a power plant temperature, and overspeed means for limiting maximum speed of the power plant.

50. In a turbine type power plant, a source of fuel under pressure, valve means for regulating the flow of fuel to the power plant, a power setting lever, normal control means operatively connected to said valve means for metering fuel ow as a function of a power plant pressure signal, a function of the setting of said lever and -a function of a power plant temperature, maximum limiting means operatively connected to said valve means for limiting fuel flow as a function of a power plant pressure signal, a function of speed and a function of a power plant temperature, and underspeed governor means operatively connected to said valve means for regulating fuel ow in predetermined speed ranges.

51. In a turbine type power plant, a source of fuel under pressure, valve means for regulating the ow of fuel to the power plant, a power setting lever, normal control means operatively connected to said valve means for metering fuel ow as a function of a power plant pressure signal, a function of the setting of said lever and a function of a power plant temperature, maximum limiting means operatively connected to said valve means for limiting fuel flow as a function of a power plant pressure signal, a function of a power plant speed and a tempera said valve means for regulating fuel llow in predetermined speed ranges.

52. In a fuel flow regulating device for a power plant, means for regulating the ow of fuel to the power plant including a servo mechanism, cam means movable in each of two directions in response to each of two parameters of power plant operation, follower 'means operative in response to movement of said cam means in one of said directions to control said servo mechanism, and means responsive to movement of said cam means in either of said directions for further controlling said servo mechanism. v

53. In a fuel control for a turbo power plant having a compressor, a combustion section and a turbine for driving the compressor, a source of fuel under pressure,

ilow controlling` means, means for lvarying the response;

of said ow controlling means to one of said signal generators for limiting the discharge pressure of said compressor, and means for regulating the pressure drop across said flow controlling means.

54. In a fuel control for a turbo power plant having a compressor, a combustion section and a turbine for driving the compressor, a source of fuel under pressure, means for delivering fuel from said -source to said combustion section, a fuel regulating mechanism, including a multiplying device operatively connected to said mechanism for metering the fuel flow, means responsive to compressor pressure for transmitting a rst signal to be multiplied to said multiplying device, means responsive to a function of speed of the power plant for transmitting a second signal to be multiplied to said multiplying device, and means responsive to a function of speed and temperature rat a predetermined point in the power plant for modifying at least one of said signals.

55. In a fuel control for a turbo power plant having a compressor, a combustion section and a turbine for driving the compressor, a source of fuel under pressure, means for delivering fuel from said source to said combustion section including 4a throttle valve, a device operatively yconnected to said throttle valve for positioning the valve and metering the fuel flow, means responsive to compressor pressure for transmitting a lirst signal to said device including operative connections thereto, means responsive to a function of speed of the power plant for transmitting a second signal to said device including operative connections thereto, said device varying the opening of said throttle valve, and means responsive to a function of speed and temperature at a predetermined point in the power plant for modifying one of said signals.

5 6. In a turbine type power plant, a source of fuel under pressure, valve means for regulating the flow of fuel to the power plant, a power setting lever, normal control means operatively connected to said valve means for regulating fuel ow as a function of a power plant pressure signal, a function of the setting of said lever and a function ot a temperature of said power plant, maximum limiting means operatively connected to said valve means for limiting the fuel flow as a function of a power plant pressure signal, a function of power plant speed and a temperature of said power plant.

57. In a fuel control for a turbo power plant having a compressor, a combustion section and a turbine for drivingA theV compressor,v asource` of' fuel under pressure-:1 means? for injecting fuel into said combustion section including speed of rotation of said power plant, adjustablelmeans for modifying the response oi said' secondmeansincluding mechanism responsive to an operativeatemperature; means operatively connectedfto said throttle-valve forimultiplying themovements of said rst and-second means and vary ing theopening of saidl throttlevalvefn proportion to the product' of' saidmovements, and means` including a servo device responsive to= compressor temperatureand another parameter of; power/plantoperation in mixed re lation and operativelyeonneetedtofsaid multiplyin g queens-k for limiting the throttle valve compressor pressure;

58'; In agus turbinev type--power-'plant,said'power plantf including al turbine, a compressor dri'vervbwthe' turbine; and av combustion chamberl producing gases; to cir-ive` the turbine, a* source -of fuelfunder pressure; means-fonregu-L lating'the flow of fuellfromisaidsourcetosaidrcombustibn chambermeans responsive'v toi at' least' compressor speed providinga signalfor controlling saidl regulatingJ means,- meansx responsive to.. compressor-speed and` a temperature. of the)power'plantupstream of the combustion chamber for providinga mixed signal, `means responsive vto -substantially the highestpressureof the gas passing' through opening in proportion to plant'. Y

the-.powerpla'nuto providea pressure: signalg. and means for multiplying saidmixedl signaland saidxpressure signal and.applying: thefresultant;v signalf Ito said yilowJ4 regulatingmeans-for` liinitingthev maximum fuel-owtolsaid power 5 9. Inla power plant"- according to claim-5 Swlerein said l temperature:responsive means is responsive toI tlie-tem` perature of the air at the inlet to said compressor.

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